Duplex loud-speaker



May 12, 1953 J. BRAMI 2,638,510

DUPLEX LOUD-SPEAKER Filed Jan. 6, 1949 V 7 I l I Z! 25 25 7 Z I '9 ll DA 2:; 26

INVENTOR.

JOSEPH BRAMI ATTORNEY Patented May 12, 1953 DUPLEX LOUD-SPEAKER JosephBrami, Baltimore, Md., assignor to Caesar David Zeitouni, Brooklyn, N. Y

Application January 6, 1949, Serial No. 69,541

23 Claims.

The invention relates to loud-speakers and more particularly tosound-chamber loud-speakers equipped with sectional reflex horns.

Loud-speakers of that type are widely used because of their compactnessand light weight.

Adequate for general applications, these loudspeakers are unfortunatelyinappropriate for high-fidelity music reproduction owing to theirrestricted sound frequency range which covers generally the high tomedium portion.

That is why they are mostly associated with large-diaphragm directradiator loud-speakers which are acknowledged as good reproducers forthe low frequency portion,

Such a combination, however, is expensive and cumbersome since itrequires the use of two separated loud-speaker units.

A first object of the invention is to convert sectional reflex hornloud-speakers into wide-range duplex loud-speakers by replacing one ofthe sections of their reflex horn (preferably the externalmouth-section) by the large diaphragm of a direct radiator loud-speakerseparately operated.

A second object of the invention is a speciallydesigned, wide-rangeduplex loud-speaker achieving the aforesaid object and comprising anumber of particular arrangements and advantageous features.

The invention, which furthermore includes other improvements, isillustrated in cross-section in the accompanying drawing in which Figure1 is the wide-range duplex loud-speaker of the present application; andFigure 2, a modified portion of the same loud-speaker.

As shown in Figure l, the wide-range duplex loud-speaker of theinvention is composed of four principal, easily-separable parts: asound-chamber reproducer I, a single-fold reflex horn 2, alarge-diaphragm direct radiator loud-speaker 3 and a double air gapmagnetic structure 4 which is common to the sound-chamber reproducer Iand to the direct radiator loud-speaker 3.

' The magnetic structure 4 consists of an annular magnet 5 clamped bybolts 6, '6 passing through its slots I, I, between a bottom of a case'8 and a ring 9 which forms an outer annular air gap In with an edge ofthe case 8 and an inner annular air gap I I with a central core I2tightly fitted to a hole of'the bottom of this case 8.

The sound-chamber reproducer I comprises a small dome-shaped diaphragmI4 which, attached to a voice coil I5 located in the inner air gap I I,has its flexible edge I6 glued between two rings I71, I I which, fittedinto a recess I3 provided by a shoulder I8 projecting the ring 9, aretightened by an exponential throat-case I9 which, screwing 2 on a thread20 of the shoulder I3, has a tapped duct 2 I and makes by its inner sidewith the facing side of the diaphragm I4, an enclosed clearance space22.

The single-fold reflex horn 2, composed of a section 23 and another 24having an annularconcave deflecting bottom 25 and mounted over thesection 23 by riveted or Welded brackets 26, 26, is screwed by itsthreaded throat 21 on the tapped duct 2| in order to communicate withthe clearance space 22 of the sound-chamber reproducer I.

The large-diaphragm direct radiator loudspeaker 3 consists of a housing28 which, welded to a rim 29 fitted and clamped by machine screws 30, 30to the magnetic structure 4, has an edge 3I to which is glued togetherwith a felt ring 32, a corrugated edge 33 of a large exponentialbell-like diaphragm 34 having an opened concave bottom 35 which,continued without contact by the exponential throat-case I3 in order toconstitute an annular-concave deflector 36, is attached to a voice coil3! guided in the outer air gap I 0 by a corrugated spider 38 glued to abottom edge 39.

The whole assembly is previously centered in order to insure theautomatic centering of the voice coil 37 of the large diaphragm 34 inthe outer air gap II), when the magnetic structure 4 fits to the rim 29.

Owing to the deflector 36, the large diaphragm 34 of the direct radiatorloud-speaker 3 serves at the same time as a continuation of thesinglefold reflex horn 2 by constituting the external mouth-section of atwo-fold, three-section reflex horn 23, 24, 34 for the sound-chamberreproducer I. The reflexed air-column of this horn 23, 24, 34(visualized by the successive arrows) follows this path; the throat 21,the section 23, the deflecting bottom 25, the space between the twosections 23 and 24, the deflector 36 and the space between the section24 and the diaphragm 34.

In the modification of Figure 2 (where the same numbers designate thesame parts as in Figure l) the wide-range duplex loud-speaker of theinvention has its sound-chamber reproducer I placed at the back of themagnetic structure 4.

For that purpose, the ring 9 is replaced by a round plate 4| holding acore 42 which, extended by a centrally-holed convex plug 43 and providedwith a tapered duct 44 ended by a tapped hole 45, forms a rear annularair gap 46 with a bottom opening of the case 8. To avoid uselessmagnetic losses, the plug 33 is made of insulating material, such asBakelite, hard rubber, plastics and the like. A back extension of thiscase-8 furnishes a shoulder 41 with a thread 48 and a recess 49 i intowhich fit the rings I1, I! supporting the municate with the clearancespace 5! of the,-

sound-chamber reproducer I.

It is obvious that the wide-range duplexrldudz speaker of the inventionnecessitates the use of. an electricalfrequency-dividing"network'whifiit by separating the sound-modulatedcurrents into two parts, permits to allocate tthemzrespecti'velyx to thevoice coil 65 of the sound-chamber. repro ducer l and to the voice coil31 of the'direct radiator loud-speaker 3.

ACCOI'diIIg-tO'thG(13116115101315 of the diaphragm" 3 4 and the =le'ngthof th'e -refiex horn '2 5 the direct radiator loud speakes 3 "and tthe-sound chambei reproducer l maybe assigned to the reproduction of theiollowing portions of-"Una soundflfrequency ran-gee- (a) the speakerstatue lovwto medium" frequonoies;--' while 'the reproducer i to thefrequencies (b)- the speake'r 3 to ma low? ire-- quenoies-y- While therepr-cducer l to the h'ighiuto medium frequencies;

O'fcOurse tHe -Ioud speaker of "th'eflinventiont is not limited to theindicated number of sections for-"the reflexhorus 1.": In: combination;a'zhell-ilike idiaphragm positionedkito .1 discharge sound-vibrationsforwardlyfrom' within the diaphragrn; means for intro ducing 'highfrequency -air vibrations rearwardlyinto the inner*partof"the diaphragmand "means for-imparting low frequency vibrations to media-- phragmr 2!In combinationv a'-smal1--sound chanmbery adiaphragm across the chamber;means fonim parting men frequency vibrations to the diaphragm a' longnarrow horn communicating "atits inner end with'. said chamberand-having itsintermediate part remote from said inner end and itslarger end adjacent to the inner "end alarge -=single' fold'exponentialdirectradiator-belllik'e'vibratorydiaphragm receivingsaid-horn and having-its inne rend: freely 'movahly "closelv-adj e centtothe larger end of" the horn: and form ing a= continuation thereof;-andmeans attached to saidinner" endofthe belllike "diaphragm for :im**parting low frequency-vibrations thereto:

31 Incombinationya'largersi-ngle fold exponen tial direct'radi'atorbell-like diaphragm 'mounted for fre'e vibration; and'h'aving asmallinnerend; means attached to saicliinnerzend' Iof thetbel-l-likeidiaphragm-forimparting lovv frequency vibrations" thereto; a;small'high" frequency sound chamber; a longnarrow refiexexponentialyhorncommuni-j I eating" atitsfsmaller end with said'johamber;and having itslarger endldisposedientirely within. said ,1 diaphragm Land.dischargingxtowarduthe inner end of .theidiaphragm; saidv diaphragmhaving its innera end,fr'eely =-movablyclosely adjacent-to the largerend of, the, horn and forming e -V. ponentialrcontinuationR of the hornwhereby said:- bell=l-iketdiaphragmiserves thesmultiplei function 1ofia: direct ,radiatorloudspeaker;- andv servesiasp. the 4 external 1mental-section. and .,an.-. exponential continuation or saidahorni a 4.1 combination; at large: single fold-g, ex-

ponential; direct radiators: belli-flikeis; diaphragm: 7 5.1

mounted for free vibration, and having a small inner end; means attachedto said diaphragm for imparting low frequency vibration thereto; a smallsound chamber to the rear of said inner end; a diaphragm across thechamber; means for imparting high frequency vibrations to the dia'phragm; a long narrow reflex exponential horn communicatingat its inner.endiwithi-said chamber anddisposed entirely within'said diaphragm andhaving its larger end discharging toward the inner end of the diaphragm;said diaphragm having its inner end freely movably closely adjacent totherlarger end of the horn and forming an exponential continuation ofthe horn; whereby said ibell'likesdiaphragnr serves the multiplefunction of a direct radiator loud speaker, and serves asthe:external'jmouthisection of an exponential continuation oi said horn.

5"." In combination, a magnet having outer and inner air gaps; adiaphragm flexibly marginally secured to--said magnet a high-"frequency-voice coil in the-inner gapand attache'd to the dia phragm; -athroatcase spaced over said dia phra-gmand having-a-duct therethrough; and anexponential f ace 1 around the duct a reflex-"horn comprisinganinnersection-mounted in'said duct, and anouter section'closed at theouter endand" sp aced from the 131181 seotion and said" f acealarge-exponential dii'ect' radi'atorsingle foldbel'l like diaphragmsubstantially' coaxialwith the h'orn and-having a-flexi-blysupportedfiaringiouter edge "and an inwardlycurved-"bottom freely-movably'closely -spaced around; and forming a con-- tinuation of, saidface; low-frequency-coil in: said outer 'airgap-attached tothe-=ihhereedg ofSthe large diaphragm:

6. In combination, a magnetic-case having a bottom and a large 'opening'opposite the' bottom; a core seoured to said bottom; an annular--magnet secured to said bottom'raroundjsaid zcorer' aa'mag' netic'r ringsecured on; said-magnet and spaced from said core and the =edgeottheopeningr to form outer and inn'erai-ragaps a" diaphragmwdispose dover the freeend 0f said core and fl'exibly secured 1 to said ring; a"high frequency-'"voice (coil in th'e' inner: gap and attached 'to:thediaphragm;- a: throattcase secured over-rsai-d" diaphragm. to: formtherewith a sound chamber and. having'am axia-ltdu'ct anda-fhaving amexponential face therearound; arbowl-lilre exponential diaphragm: ham:

1 ing "am inner margin freely movablmaround said face andforming-an:exponentiat continuationaof thexfaoe; means tfo'rzrimpartingilowrfrequenoy-wi brations to said inneramargin: of thezdiaphragm'atancexponenti'al-*reflexahorn: having: its small end inzrsaid ductyandits; large; end .di'reoted.;- towardi said'zfaceei 7 lntcombination',"a. member having;- a ducts therethrough; andcan exponential face-aroundthe duct? a reflex: norm-comprising," an inner-rsection-'- seourediat'itsinner endinzsaid duct, ;and an;outer section spacedzzaround {theinner :sectiomandtexs 1 tendingto nean'said 1f aces-and havingsat; theouter end 1 an end-icaps spaced'ifromi th-BFiIlHBI rsectiongw a!large-"exponential idirect radiator tsinglesfold 1 bell-like w diaphragmsubstantiallw coaxial with;

secured to said bottom and terminating substantially centrally of saidopening in the plane of the opening; an annular magnet secured to saidbottom around and spaced from the core and terminating near said plane;a magnetic ring secured on said magnet and spaced from said core and theedge of the opening to form outer and inner air gaps; a dome-shapeddiaphragm disposed overv the free end of said core and having a.flexible marginal extension secured to said ring; a, high frequencyvoice coil attached to the edge of the diaphragm and disposed in theinner air gap; an exponential throat case marginally secured to saidring over and conformably spaced from said diaphragm to form therewith asound chamber and provided with an axial duct communicating with thesound chamber, and an exponential face around the duct; a bowl-likediaphragm having a freely movable inner margin forming a continuation ofsaid face; a horn having its small end in said duct and its large enddirected toward said face; and a low frequency voice coil attached tothe inner edge of the large diaphragm and disposed in said outer airgap.

9. In combination, a member having a duct and an exponential face aroundthe duct; a single fold reflex horn comprising an inner section taperingtoward and secured at its inner end in said duct, and an outer sectionspaced from and enclosing the inner section and flaring toward andextending to near said face of the member and having at the outer end anend cap having an inner concaved face facing and spaced from the innersection; a bell-shaped loud speaker housing substantially coaxial withthe reflex horn and having an inner end secured fast on said memberaround said face and having at its free edge a belt ring disposed in aplane transverse to the axis of the horn slightly beyond the outer endof the horn; a large exponential direct radiator single fold bell-likediaphragm conformably spaced from the loud speaker housing and having atransversely outwardly disposed flexible edge secured to said belt ringand a downwardly inwardly curved inner margin freely movably closelyspaced around the edge of and forming a continuation of said face of thethroat case; means connected to said inner margin for imparting lowfrequency vibrations to the large diaphragm; and means for supplyinghigh frequency vibrations in said duct.

10. In combination, a magnetic case having a bottom having a largecentral opening and a larger opening in the top; a core spaced in saidlarge opening of said bottom to form an inner air gap and terminatingsubstantially centrally of said larger openin in the plane of the largeropening, and having an axial duct therethrough; an annular magnetsecured to said bottom around and spaced from the core and terminatingnear said plane; a magnetic ring secured on said magnet and around theupper end of said core and spaced from the edge of said large opening toform an outer air gap; a convexed plug mounted on the rear end of thecore and having a duct alined with the duct of the core; a dome-shapeddiaphragm conformably disposed over the plu conformably spaced from saidplug to form therewith a sound chamber and communicating with saidducts, a high frequency coil attached to the diaphragm and disposed inthe inner air gap; a freely vibratory bell-shaped diaphragm having a lowfrequency coil secured to its inner end and disposed in said outer gap;and a horn having a small end in said duct, and a large end in saiddiaphragm.

11. In combination, a small sound chamber; a diaphragm across thechamber; means for imparting high frequency vibrations to the diaphragm;a single fold horn comprising an inner horn section tapering toward andcommunicating with said chamber, and an outer horn section spaced fromand enclosing the inner section and flaring toward and spaced from saidinner end and having at the outer end an end cap having an innerconcaved face facing and spaced from the inner section; a largeexponential direct radiator single fold bell-like diaphragm having adownwardly inwardly upwardly curved bottom freely movably closely spacedaround the inner end portion of said inner section and formingexponential continuation of the outer section; and means attached to theinner part of the large diaphragm for imparting low frequency vibrationsthereto.

12. In combination, a large direct-radiator diaphragm mounted for freevibration, and having a large outer end and a small inner end; means forimparting low frequency vibration to said diaphragm; a high-frequencychamber; a narrow horn communicating at its smaller end with saidchamber and having its larger end near and forward of and discharginginwardly toward and against the inner face of the inner end part of thediaphragm; said diaphragm forming a continuation of the horn andreflecting the sound waves received from the horn; whereby said belllikediaphragm serves the multiple function of a reflector and as a reflexwall for the horn and as a direct radiator loud speaker, and serves asthe external mouth section and continuation of said horn.

13. In combination, a large single fold exponential direct radiatorbell-like diaphragm mounted for free vibration, and having a large outerend and a small inner end; means attached to said diaphragm forimparting low frequency vibration thereto; a small high frequencycompression chamber; a long narrow exponential horn communicating at itssmaller end with said chamber and disposed within said diaphragm andhaving its larger nd near and forward of and dischargin toward the innerend of the diaphragm; said diaphragm having its inner end freely movablyclosely adjacent to the larger end of the horn and forming anexponential continuation of the horn and reflecting the sound wavesreceived from the horn; whereby said belllike diaphragm serves themultiple function of a reflector and as an outer reflex wall for thehorn and as a direct radiator loud speaker, and serves as the externalmouth section and as an exponential continuation of said horn.

14. In combination, a horn; means for introducing air vibrations intothe horn; a hollow diaphragm mounted for free vibrations independentlyof the horn and positioned with its inner side facing the mouth of thesaid horn to form a reflex contiuation of and an external mouth sectionfor the horn; and means for imparting vibrations to the diaphragm.

15. In combination, a horn; means for introducing high frequency airvibrations into the horn; a hollow direct radiator diaphragm mounted forfree vibrations independently of the horn and positioned with its innerside facing the mouth of the said horn to form a reflex continuation ofand an external mouth section of the horn; and additional means forimpart- :acsaiero ing low '--rrequency' vibrations tovthe' diaphragm.16.. In combination, a vibratory "diaphragm :positioned to direct soundvibrations forwardly -from thezffront fa-certhereof; means for impart-'ing sound vibrationsto .the;:diaphragm for :pro-

:jecting. the -.vioration's forwardly; an additional source \ofxsoundvibrations; a horn communicating:at itsxsmaller end with said sourceand'having .its larger end near anddirected-rearwardly toward the.intramarginal part of the forward face: oi-ithe diaphragm, to :projectthe vibrations from the :horn rearwardly "from said larger end againstthesdiaphragm'to be combined with-the 'vibrationssthereof, "to bereflected by the v.dia-

"phragm, and: proj ected'with them forwardly from ithleifaifle' of thediaphragm.

.=1:7.. In combination, a concaved vibratory diaphragm positioned. todirect sound vibrations ior- "wardlytr'romcthe concaved race thereof;means for-imparting low frequency sound vibrations I to the diaphragmfor projecting the low frequency vibrations forwardly .fromsaid concavedface;: .asource of high frequency sound vibrations; a :horncommunicating'at its smaller end with said. source and having its largerend near :and :directed. irearwardly toward :the 'mid part oftheuforwardconcavedface of the-diaphargm,

.to project the high frequency vibrations rear-- *wardly from saidlarger end against the dia- ,phra gm tobe reflected bythe diaphragm,added 130 13116110! frequency vibrations and projected "with themtogether forwardly from the forward .face "of the" diaphragm.

-l8..-In.combination, aibell-like vibratory diayphragm positioned todirect sound vibrations .iorwardly from the: concaved race thereof meansfor imparting low irequency sound vibrations to the inner part of thediaphragm forprojecting the low frequencyvibrations'iorwardly; :a sourceof high frequency sound vibrations; :a horncommunicating at its smallerend with said :source and having-its larger end near and directed rear-Wardlytoward the mid-part of the forward face of the bell-likediaphragm, to project the high frequency vibrations rearwardly-from saidlarger end against the diaphragm.

.19. In combination, a vibratory diaphragm positioned to direct soundvibrations forwardly from .its forward. .face thereof; means for. im-.-.parting low frequency sound vibrations. to. the diaphragm fOrprojecting the low frequency vi brations forwardly; a source of .highfrequency sound vibrations; a long narrow horn communicating atits.innerend with said sourceandhav- .ing its intermediate part remote fromsaid inner .end' and its larger end adjacent .to its inner rend I .and'directed .rearwardly toward the. mid-part.of thejorward faceof thediaphragm, to project the high frequency vibrations rearwardly from saidlarger. end against. the diaphragm to be reflected by the.diaphragmcombined with the low ...fre,quency vibrations and projectedwith them forwardly.

20. In combination, ,a. high frequency sound chamber; a longnarrowhorncommunicatingat its. smaller end with said.chamber;..a.largedirect radiator concaved vibratorydiaphragm receiving the larger end andintermediate ,part of said-horn'and having its inner part-freely mov-=ably closely adjacent to "the larger "end "of "the horn; :arrdmeansattached :torsaid send-:of

the; :diaphragm for imparting: low frequency avibrations-zthereto. I

21. In combination, .alsound chamber; :a long narrow horn communicating:at its smaller :end

with; said chamber and having its larger: end radjacent tothezinnerzend; a large .concavedzd'irect radiator vibratory diaphragmreceiving; saidcends initsv concavity and. havinginner part'moyably-closely adjacent to :the :larger end of the .rhorn and forming a'continuatiomthereof and. means attached to the diaphragm .for impartingvibrations thereto.

.22. In :combination, a high frequency .soun

.' chamber; along :na-rrow horn:communicatingat .its: inner end with;said. chamber and having its intermediate part .remotezrrom 'saidinn-eriend and its larger end adjacent -.to the-innerxend;

a Iargedirect radiator bell-like vibratory diaphragm receiving *saidhorn in the space be tween theinnerand outer ends of the diaphragmandhaving-its innerend freely movablyrlosely adjacent-to the larger endof the. horn and forming-a continuation'of, and external mouth for,

\ the. horn; and means-attached to, said inner end ofv the diaphragmfor-imparting low frequency vibrations thereto.

23. In -.combination, a concaved bell-like :loW frequencyvibratorydiaphragm positioned to direct sound vibrations forwardly fromthe 'con- .caved .face thereof; low frequency means -operativelyconnected to the mid-part of therdialphragmflfor imparting low frequencysound vibrations to the diaphragm for projecting the .low frequencyvibrations forwardly from said concaved face;v a separatesource or highFire.-

guency sound vibrations additional-to said 10w .frequencymeans; a horncommunicating atl-ts smallerrendwith said source andhaving its largerend-.near and directed .rear-wardiy toward the mid-part of the forwardconcaved face of the .diaphragm, to project thehigh frequencyvibrationsrearwardly from said larger end. againstithe vibrating lowfrequency diaphragm to be re- .iflectedby the low frequencydiaphragmadded to and combined withthe low frequency vibrations andprojected in combination with them forwardly from the forward face ofthe dia- ,phragm,. as. anintegralvibration, thusgiving unifieid, firm,.musical tone pattern.

JOSEPH BRAMI.

References Cited in the file of thispatent UNITEDSTATES PATENTS

